第56卷 第3期 古 脊 椎 动 物 学 报 pp. 248–263 2018年7月 VERTEBRATA PALASIATICA figs. 1–3 DOI: 10.19615/j.cnki.1000-3118.180403 Fossil gibbons (Mammalia, Hylobatidae) from the Pleistocene of Chongzuo, Guangxi, China ZHANG Ying-Qi1,2,3 JIN Chang-Zhu1,2 WANG Yuan1,2 Alejandra ORTIZ4 HE Kai5,6 Terry HARRISON7 (1 Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chines Academy of Sciences Beijing 100044 [email protected]) (2 CAS Center for Excellence in Life and Paleoenvironment Beijing 100044) (3 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Nanjing 210008) (4 Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University Tempe AZ 85287, USA) (5 Kunming Institute of Zoology, Chinese Academy of Sciences Kunming 650223) (6 The Kyoto University Museum, Kyoto University Kyoto 606-8417, Japan) (7 Center for the Study of Human Origins, Department of Anthropology, New York University New York NY 10003, USA) Abstract Recent fieldwork at Pleistocene cave sites in the Chongzuo area in Guangxi Zhuang Autonomous Region has yielded 33 isolated teeth of fossil hylobatids. Comparisons indicate that the teeth can all be referred to a single species of Nomascus, but the material is insufficient to assign it to a particular species. The molars are slightly larger on average than those of extant species of Nomascus, but unlike contemporary great apes from the Pleistocene of southern China, the hylobatids do not seem to have undergone a change in dental size through time. Nomascus is not present in the Chongzuo area today, but historical records indicate that the genus may have been widely distributed across southern China in the recent past. Key words Chongzuo, Guangxi; Pleistocene; Nomascus; taxonomy; isolated teeth; evolution; dental size Citation Zhang Y Q, Jin C Z, Wang Y et al., 2018. Fossil gibbons (Mammalia, Hylobatidae) from the Pleistocene of Chongzuo, Guangxi, China. Vertebrata PalAsiatica, 56(3): 248– 263 1 Introduction Extant hylobatids (gibbons and siamangs) are currently included in four genera: Hylobates, Hoolock, Nomascus, and Symphalangus (Mittermeier et al., 2013; Roos, 2016; Rowe and Myers, 2016). The phylogenetic relationships between these taxa have not been fully resolved (Meyer et al., 2012; Wall et al., 2013; Carbone et al., 2014; Harrison, 2016), but the molecular clock estimates indicate a date of ~20–17 Ma for the divergence of hylobatids from the other hominoids, and ~9–5 Ma for the divergence of the crown hylobatid lineages (Fabre et al., 2009; Matsudaira and Ishida 2010; Thinh et al., 2010; Chan et al., 2010, 2012; Perelman 中国科学院战略性先导科技专项(编号：XDPB05)、国家自然科学基金(批准号：41625005)、现代古生物学和 地层学国家重点实验室(中国科学院南京地质古生物研究所) (编号：173132)和纽约大学资助。 收稿日期：2017-10-23 Zhang et al. - Fossil gibbons from the Pleistocene of Chongzuo 249 et al., 2011; Israfil et al., 2011; Springer et al., 2012; Finstermeier et al., 2013; Carbone et al., 2014; Pozzi et al., 2014). However, the fossil record of hylobatids is meager (Harrison, 2016). The family appears to have originated some time during the Early Miocene, but the only known stem hylobatid is Yuanmoupithecus xiaoyuan from the Late Miocene (~7–9 Ma) of Yunnan (Pan, 2006; Harrison, 2010, 2016). Otherwise, fossil hylobatids are known from Pleistocene localities in China, Vietnam, Thailand, Laos, Borneo, Sumatra, and Java (Harrison, 2016). These are mostly isolated teeth, making their taxonomic positions and phylogenetic affinities difficult to determine, but they can generally be assigned to extant genera. Today, gibbons in China (Hylobates, Hoolock, and Nomascus) are restricted to the southwest of the country including Tibet, Yunnan, Guangxi, and on the island of Hainan (Ji and Jiang, 2004; Geissmann, 2007; Fan and Huo, 2009; Mittermeier et al., 2013; Fan et al., 2017), but during the Pleistocene, and even in historic times, they were widely distributed across southern and central China (van Gulik, 1967; Groves, 1972; Gao et al., 1981; Gu, 1989; Geissmann, 1995; Gu et al., 1996; Jablonski et al., 2000; Jablonski and Chaplin, 2009; Harrison, 2016), gibbons have been largely extirpated in China within the last several hundred years because of the high level of anthropogenic pressure (Turvey et al., 2015). The best-known hylobatid from the Pleistocene of China is a partial mandible with m2 and m3 from Yanjinggou in Chongqing Municipality (formerly part of Sichuan Province), described by Matthew and Granger (1923) as Bunopithecus sericus. A recent reanalysis of the specimen (Ortiz et al., 2015) has shown that Bunopithecus represents a distinct genus and is possibly the extinct sister taxon of Hoolock. Other Pleistocene hylobatids from China have been recovered from Yunnan, Guangxi, Hainan, Sichuan, Guizhou, Guangdong, and Hunan (Gu et al., 1996; Jablonski and Chaplin, 2009). Gu (1986, 1989) published an account of hylobatid finds from Guangxi obtained under the direction of Pei Wen-Zhong (Pei Wen-Chung) in 1956–1957. The 37 isolated teeth, consisting primarily of upper molars, came from at least eight different cave sites, as well as medicinal supply companies. Gu concluded that the majority of the upper molars resembled Nomascus concolor (sensu lato) in retaining a lingual cingulum, while three upper molars lacking a lingual cingulum were more similar to Hoolock. Extant Hoolock species are distributed west of the Salween River from Bangladesh to western Yunnan, while N. concolor is distributed in Yunnan as well as in Laos and Vietnam. Neither species is currently found in Guangxi, although N. nasutus occurs in western Guangxi. Recent fieldwork in the Chongzuo area in Guangxi Zhuang Autonomous Region (ZAR) has yielded a sample of isolated teeth of fossil hylobatids from eight cave sites that date from Early to Late Pleistocene (Fig. 1). Gibbons appear to be a rare component of the Pleistocene primate community in Chongzuo, constituting less than 1% of specimens (Takai et al., 2014). The aim of this contribution is to describe the newly discovered hylobatids from Chongzuo and to determine their taxonomic positions. 250 Vertebrata PalAsiatica, Vol. 56, No. 3 Fig. 1 Map of the Chongzuo area showing the location of the cave sites with hylobatid fossils 2 Materials and methods The new fossil hylobatid specimens were recovered from cave sites in the area of Chongzuo in Guangxi ZAR. They consist of 33 isolated teeth, mostly upper and lower molars (Fig. 2; Table 1). All of the specimens are housed in the collections of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (IVPP). The ages of the specimens range from late Early Pleistocene to Late Pleistocene. The oldest specimens are from Baikong Cave, with an estimated age of ~2.0 Ma (Jin et al., 2014; Takai et al., 2014). The fossils were compared with extant hylobatids from the American Museum of Natural History in New York, the Smithsonian Institution in Washington D.C., the Natural History Museum in London, the Kunming Institute of Zoology in Kunming, the Institute of Zoology in Beijing, and the Biology Museum, School of Life Sciences at Sun Yat-Sen University in Guangzhou. Metrical and morphological comparisons indicate that the fossils can all be referred to a single species within the genus Nomascus. Zhang et al. - Fossil gibbons from the Pleistocene of Chongzuo 251 Fig. 2 Teeth of Nomascus sp. from the Chongzuo area in occlusal view Baikong: 1. PA 1632, right M3, 2. PA 1633, left M3; Sanhe: 3. PA 1634, right M1, 4. PA 1635, right M1; Daxin Hei: 5. PA 1636, left M2, 6. PA 1637, right M3, 7. PA 1638, left P4; Yixiantian: 8. PA 1639, right M1, 9. PA 1640, left M1, 10. PA 1641, left M1 or M2; Shuangtan: 11. PA 1642, left M2, 12. PA 1643, left m2; Zhiren: 13. PA 1644, left M1 or M2, 14. PA 1645, left M1 or M2, 15. PA 1646, left M2; Yugong: 16. PA 1647, left M2, 17. PA 1648, right M1; Baxian: 18. PA 1649, right P4, 19. PA 1650, left P3, 20. PA 1651, right M2, 21. PA 1652, right m1 or m2, 22. PA 1653, right m3, 23. PA 1654, right m2, 24. PA 1655, left M2, 25. PA 1656, left M1 or M2, 26. PA 1657, left M1 or M2, 27. PA 1658, left M1, 28. PA 1659, left M2, 29. PA 1660, right M2, 30. PA 1661, right M2, 31. PA 1662, right M3, 32. PA 1663, right M3, 33. PA 1664, left M1 or M2 Isolated upper and lower first and second molars of hylobatids are difficult to discriminate from each other, and in these instances the fossils are described as M1 or M2 and m1 or m2 (see Table 1). In other cases, however, it is possible to assign molars, with reasonable confidence, to their appropriate serial position based on morphological criteria. Measurements of the specimens are presented in Table 1. Molar terminology follows Harrison and Gu (1999) (Fig. 3). Fig. 3 Molar terminology used in this study Left m2 (A) and left M2 (B) of Nomascus concolor (Kunming Institute of Zoology 024165) Mesial is top, lingual is right on m2 and left on M2 (after Harrison and Gu, 1999) 252 Vertebrata PalAsiatica, Vol. 56, No. 3 Table 1 Dimensions of hylobatid teeth from Chongzuo, Guangxi (mm) Age Locality Field no. IVPP no. Teeth MD BL Early Pleistocene Baikong CLBBD201011-1040 PA 1632 RM3 5.8 6.5 (~2.0 Ma) CLBBD201011-931 PA 1633 LM3 6.1 Early Pleistocene Sanhe GCSD0605-1 PA 1634 RM1 6.5 (~1.2 Ma) GCSD0410-001 PA 1635 RM1 6.2 7.0 Middle Pleistocene Daxin Hei DLZNH201206-30 PA 1636 LM2 7.0 8.1 (~380–310 ka) DLZNH201211-105 PA 1637 RM3 5.6 6.7 DLZNH201211-820